Assessment of Stroke Volume and Cardiac Output in Response to Varying Heart Rates
For patients and families
In plain language
An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.
- What is being studied
- The protocol lists: Pacing.
- Who it may be relevant to
- Registry conditions: Vasovagal Syncope. Basic parameters: 18 years — 70 years · All.
- What needs checking
- Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
- Where it takes place
- Canada
- Next step
- Save the trial, show it to the treating physician, and confirm current recruitment with the study center. Costs, documents and travel →
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Official title
Assessment of Stroke Volume and Cardiac Output in Response to Varying Heart Rates and Body Position - a Pacemaker Based Study
Overview
The investigators will seek to determine the effects of different heart rates on both stroke volume and cardiac output using non-invasive hemodynamic assessments. In order to safely manipulate the HR, the investigators will study patients with permanent pacemakers in whom heart rate manipulation can be done in a safe and non-invasive manner.
Detailed description
Permanent pacemakers have sometimes been used to treat patients with recurrent vasovagal syncope. This is because patients with vasovagal syncope often experience bradycardia at the time of their syncope. Unfortunately, pacemakers are often ineffective in preventing syncope.
Classical cardiovascular hemodynamics would suggest that increasing the heart rate (HR; via pacemaker) should increase the cardiac output (CO). This is because:
CO = HR x Stroke volume (SV).
The assumption is that the SV is fixed during manipulation of the HR. However, this might not be the case. As the number of beats per minute (HR) increases, the cardiac cycle length (R-R interval \[RRI\]) shortens, as a function of simple math. This means that the time in cardiac systole shortens, and the time in cardiac diastole shortens. Since cardiac diastole is when the heart fills up with blood, faster HR can be associated with decreased cardiac filling times. This, in turn, could compromise the SV. However, there is a paucity of data as to what happens to SV and CO at different HR. Further, it is possible that these effects will be different when a person is lying down supine versus when a patient is upright (when stroke volume will be lower).
The investigators will seek to determine the effects of different HR on both SV \& CO. In order to safely manipulate the HR, they will study patients with permanent pacemakers in whom HR manipulation can be done in a safe and non-invasive manner.
Interventions
- Device Pacing
Assess the non-invasively determined stroke volume and cardiac output response at different paced heart rates in patients with a cardiac pacemaker or implanted defibrillator with preserved ejection fractions (LVEF≥50%)
Primary outcome measures
- Change in cardiac output while atrial pacing at lower and higher rates while supine [Time frame: 1 day]
Secondary outcome measures (7)
- Change in cardiac output at lower and higher ventricular (VVI) paced rates while supine [Time frame: 1 day]
- Change of cardiac output at lower and higher atrial (AAI) paced rates while supine versus while upright [Time frame: 1 day]
- Change of cardiac output at lower and higher ventricular (VVI) paced rates while supine versus while upright [Time frame: 1 day]
- Change in stroke volume at lower and higher atrial paced rates while tilted up [Time frame: 1 day]
- Change in stroke volume at lower and higher ventricular (VVI) paced rates while tilted up [Time frame: 1 day]
- Change of stroke volume at lower and higher atrial (AAI) paced rates while supine versus while upright [Time frame: 1 day]
- Change of stroke volume at lower and higher ventricular (VVI) paced rates while supine versus while upright [Time frame: 1 day]
Eligibility criteria
Inclusion criteria
- Age 18-70 years (inclusive)
- Implanted permanent pacemaker or implanted defibrillator capable of atrial and ventricular pacing
- LV ejection fraction >50%
Exclusion criteria
- Unable or unwilling to provide informed consent
- Clinical need for a cardiac resynchronization device
Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.
Healthy volunteers: No
Study design
- Allocation
- N/A
- Model
- Single group
- Masking
- Open label
- Primary purpose
- Treatment
Study locations
Canada · 1 center
- University of Calgary — Calgary
Identifiers
NCT: NCT03446326 · REB15-2887